It would be really useful to have a way to tell a layer to only export to the json data file and not to the sprite sheet itself. Maybe Right Click the layer and Convert To → Data Object.
Small bump: Added a video to explain this idea a little better. I kind of use Aseprite as a bit of a psuedo level editor and it would be really useful to export the layer information associated with a layer but not export it into the sprite sheet. https://youtu.be/TXESJNbS77E